80 results about "Gas pressure sintering" patented technology

The invention relates to the technical field of high-performance structural ceramic materials and corrosion resistance optimization thereof, in particular to a preparation method of high-performance silicon nitride ceramic, which realizes performance improvement through dynamic optimization of a composite sintering aid, closed-loop regulation and control of air pressure sintering and multi-process data linkage. In the raw material pretreatment stage, a laser particle size analyzer is adopted for monitoring particle size distribution in real time, surface modification parameters are adjusted in a linkage mode, and a uniform monomolecular coating layer is formed; the proportion of rare earth oxide and aluminum oxide in the composite sintering aid is dynamically adjusted according to the fluctuation of the mixing torque, and agglomeration and segregation of the aid are inhibited. And in the air pressure sintering stage, the argon pressure and the heating rate are dynamically adjusted based on the slope of a shrinkage curve, and directional arrangement of beta-phase grains is promoted by combining low-temperature nitrogen protection and high-temperature argon densification. And multi-dimensional process control synergistically optimizes grain boundary components, structure and density, so that the corrosion resistance and the service life of the silicon nitride ceramic in a sulfur-containing environment are remarkably improved and the service life of the silicon nitride ceramic in the sulfur-containing environment is remarkably prolonged.

The invention provides a preparation method of a high-performance silicon nitride ceramic substrate, and relates to the field of production and preparation of silicon nitride ceramic substrates, and the high-performance silicon nitride ceramic substrate comprises the following raw materials by weight: 40-130 parts of silicon nitride powder, 20-110 parts of an organic solvent, 3-15 parts of a sintering aid, 5-15 parts of a binder, 2-6 parts of a plasticizer, and 1-6 parts of a dispersant. A tape casting method is adopted, the silicon nitride ceramic substrate is prepared through glue discharging and air pressure sintering, and the silane coupling agent, the silicon powder, the beta-phase silicon nitride powder, the silicon carbide whiskers and other ingredients can remarkably improve the strength and the thermal conductivity of the silicon nitride ceramic substrate.

The invention discloses a carbon ceramic composite conductive microsphere, a ceramic resistor and a preparation method, and belongs to the technical field of production of special materials of electrical equipment, and the method comprises the following steps: sequentially dipping porous mullite in a precursor solution of carbon and slurry containing carbon black, and carrying out drying treatment and carbon burying sintering to obtain the carbon ceramic composite conductive microsphere; the preparation method comprises the following steps: preparing a ceramic raw material, performing vacuum-assisted centrifugal impregnation on the ceramic raw material and slurry consisting of a binder in pug consisting of the ceramic raw material and a surfactant, sequentially performing drying and glue discharging treatment, primary isostatic pressing forming and air pressure sintering, cooling to room temperature, and performing mechanical treatment and electrode spraying to obtain the ceramic resistor. Impregnation improves the dispersibility and uniformity of the carbon material in the porous mullite to form a continuous conductive path, the carbon black-containing slurry improves the conductivity of the ceramic resistor, carbon-buried sintering generates in-situ carbon with abundant types, the combination of carbon and a ceramic interface is promoted, and the oxidation resistance, mechanical properties and electrical properties of the ceramic resistor are improved.

The invention discloses a rare earth oxide modified high-entropy hard alloy and a preparation method thereof. A high-entropy hard phase (high-temperature calcination), a high-entropy binding phase and rare earth oxide are adopted, grinding, pressing and air pressure sintering at the temperature of 1450-1550 DEG C are conducted, and the high-entropy hard phase is prepared from tungsten carbide, titanium carbide, zirconium carbide, yttrium carbide, manganese carbide, chromium carbide and molybdenum carbide; the high-entropy binding phase comprises the following components: cobalt and a CoCrFeNi-series high-entropy alloy; and the component of the rare earth oxide is Y2O3 or Nd2O3. The prepared rare earth oxide modified high-entropy hard alloy has the advantages of high strength, high compactness, high hardness, high wear resistance and the like.

The invention belongs to the technical field of ceramic materials, and discloses a wave-transparent bulletproof ceramic material and a preparation method thereof. The ceramic material comprises the following components in parts by weight: 60-80 parts of alumina micro powder, 20-40 parts of silicon nitride powder, magnesium carbonate powder, lanthanum oxide powder, a polyethylene glycol dispersant, a temporary binder emulsified paraffin and glycerol. The preparation method comprises the following steps: mixing and stirring the raw materials, and fully pulping; grinding and dispersing the slurry through a high-speed grinder; carrying out spray granulation on the slurry by adopting a centrifugal spray granulation tower, and preparing the slurry into composite granulation powder; pressing the granulation powder into a required shape to obtain a green body; and a high-temperature nitrogen gas pressure sintering furnace is adopted for product sintering. The bulletproof ceramic disclosed by the invention has the advantages of low dielectric constant, high toughness and high hardness, and normal communication signal transmission is not influenced while the bulletproof ceramic has excellent protection performance.

The invention provides a method for preparing a high-performance silicon nitride ceramic ball based on a pressure modulation sintering technology, and relates to the field of functional ceramic material preparation, and the method comprises the following steps: 1, preparing a green body; 2, PMS sintering is carried out; step 3, cooling; traditional high-performance silicon nitride ceramic balls (the relative density is required to be larger than 99%, the Vickers hardness is required to be larger than or equal to 1500 kgf / mm, the bending strength is required to be larger than or equal to 920 MPa, and the fracture toughness is required to be larger than or equal to 6.0 MPa.m / ) are mainly prepared through a two-step process of normal pressure / air pressure sintering (GPS) and hot isostatic pressing (HIP). Although high densification of the material can be realized, the method has the problems of complicated process flow, high energy consumption, long production period, high equipment occupancy rate and the like.

The invention discloses ceramic containing an air cooling structure and a preparation method and application thereof. The method comprises the following steps: uniformly mixing a sintering aid and ceramic powder, embedding the mixture into a template for pre-pressing molding, sintering at high temperature, and removing the template by adopting a high-temperature oxidation method (800-1000 DEG C, 1-3 hours) combined with a sand blasting auxiliary method (the sand blasting pressure is 0.2-0.8 MPa, and the sand blasting time is 1-5 minutes) to form a through air cooling channel; for ceramic powder easy to react with the template, spraying a boron nitride coating of 5-20 microns on the surface of the template to prevent interface reaction; various sintering modes (such as air pressure sintering and spark plasma sintering) and template shapes (such as a straight-through type and a spiral type) are supported, the structural controllability is good, channels are removed cleanly, and the process is simple; the obtained ceramic has excellent thermal management capability while maintaining high density and mechanical properties, and is suitable for high thermal load environments such as hot end parts of aerospace engines and the like.

The invention discloses a preparation method of high-purity aluminum nitride single crystal powder. The method comprises the following steps: uniformly mixing raw materials aluminum powder and aluminum nitride powder according to a ratio, putting the mixture into an air pressure sintering furnace, vacuumizing, introducing high-pressure argon, heating to a set temperature, introducing nitrogen, carrying out a fire blast reaction, cooling to room temperature, and crushing to obtain the high-purity aluminum nitride single crystal powder with D50 of 20-200 microns. According to the method, the synthesis of the coarse-particle high-purity aluminum nitride single crystal powder is realized by utilizing the rapid nitridation explosion reaction of the aluminum powder in the high-temperature and high-pressure nitrogen, the method has the characteristics of simple process and low preparation cost, and the prepared high-purity aluminum nitride single crystal powder can be used as a high-thermal-conductivity filler for electronic packaging.

The invention belongs to the technical field of electronic ceramic substrate materials, and particularly relates to a preparation method of a microcrystalline glass composite silicon nitride ceramic substrate, which is prepared from the following raw materials: 1-5% of alpha-phase silicon nitride powder, 86-95% of beta-phase silicon nitride powder, 0.2-3% of metal silicon powder, 2.5-8% of glass powder and 1.3-8% of metal oxide. The preparation method comprises the following steps: S1, mixing and grinding raw materials to obtain ceramic slurry; s2, adding Arabic gum into the ceramic slurry as a binder, and carrying out spray granulation; granulation powder is obtained; s3, carrying out dry pressing molding and cold isostatic pressing treatment on the granulation powder to prepare a ceramic plate blank; and S4, sintering and crystallizing the ceramic plate blank. According to the invention, the glass ceramic powder is introduced as a sintering aid and a second phase, and the sintering temperature of the silicon nitride is obviously reduced from the conventional temperature of more than 1800 DEG C to 1500 DEG C by utilizing the liquid phase effect of the glass ceramic powder in the sintering process, so that two modes of air pressure sintering and normal pressure sintering can be used, and the energy consumption and the requirements on equipment are reduced.

The invention belongs to the technical field of production of special materials for electrical equipment, and particularly relates to a ceramic resistor containing a continuous conducting layer and a preparation method and application thereof. According to the preparation method provided by the invention, the conductive material is deposited in the fibrofelt supporting layer by adopting vacuum impregnation-air pressure sintering, then the ceramic material is deposited in the supporting layer containing the conductive layer by adopting vacuum impregnation-air pressure sintering, and all the structural layers are continuously communicated to form the novel ceramic resistor. According to the invention, the fibrofelt is used as the supporting layer, and the carbon nanotubes can be uniformly and continuously dispersed through in-situ generation of the carbon nanotubes in the supporting layer, so that a conductive channel is formed, and the resistivity is effectively reduced; meanwhile, the fiber felt is impregnated with ceramic mixed slurry and is subjected to air pressure sintering, so that the apparent porosity can be effectively reduced, and the volume density is increased. Therefore, the ceramic resistor prepared by the invention has good electrical properties, excellent mechanical properties and good use stability, and is suitable for industrial application as a closing resistor material.

The invention discloses a silicon nitride ceramic formula and a preparation process of a bearing roller matched with the silicon nitride ceramic formula, belongs to the technical field of ceramic materials, and aims to solve the problem of rolling contact fatigue failure caused by insufficient fracture toughness and microscopic crack propagation of an existing silicon nitride bearing roller under high-speed and heavy-load working conditions. The core formula of the invention comprises an alpha-Si3N4 matrix, a composite rare earth additive, a nano TiC modifier and an MgO heat conduction enhancer. The fracture toughness and fatigue resistance of the material are remarkably improved through process nano powder ultrasonic pre-dispersion, closed nitrogen circulation spray granulation, two-step air pressure sintering and cryogenic-thermal tempering gradient stress treatment.

The application discloses a low-temperature normal-pressure sintering preparation method of silicon nitride ceramic for high-power electrothermal elements, and comprises the following steps: (1) mixing silicon nitride powder and nitride glass sintering additives, wherein the amount of the silicon nitride powder is 60%-93% based on the total weight of the mixed raw materials, and the amount of the nitride glass sintering additives is 7%-40%; (2) drying the mixture obtained in the step (1) to obtain dry materials; (3) forming the dry materials obtained in the step (2) to obtain formed materials; and (4) sintering the formed materials obtained in the step (3) under normal pressure. According to the method, the sintering temperature is reduced to a low-temperature interval of 1550-1680 DEG C by using the nitride glass sintering additives, the dependence on expensive and complex hot-pressing or gas-pressure sintering equipment is eliminated, the normal-pressure sintering of high-performance silicon nitride ceramic is realized while the energy consumption and cost are significantly reduced, and a process foundation is laid for large-scale and low-cost manufacturing.

The invention relates to a long-column-shaped beta-Si3N4 crystal grain controllable growth ceramic ball material and a preparation method of the long-column-shaped beta-Si3N4 crystal grain controllable growth ceramic ball material. The material is prepared by taking alpha-Si3N4 powder as a matrix and adding beta-Si3N4 seed crystal and a composite sintering aid in a specific proportion through a multi-stage air pressure sintering process. The formula comprises the following components in parts by weight: 80-95 parts of alpha-Si3N4 powder, 1-20 parts of beta-Si3N4 seed crystal and 3-10 parts of a composite sintering aid, wherein the composite sintering aid consists of R2O3 (R is at least one of Y, Ce and Lu) and Al2O3. Through seed crystal induction and sintering process control, controllable growth of the size, the length-diameter ratio and the spatial distribution of long columnar beta-Si3N4 crystal grains in the ceramic ball is realized, and the prepared silicon nitride ceramic ball has excellent performances of high toughness, high strength, long service life and the like; and the method is suitable for high-end equipment fields such as high-speed bearings, precision machine tools and wind power generation equipment.

The invention belongs to the technical field of preparation of ceramic materials, and particularly relates to a method for toughening silicon nitride ceramic through coprecipitation coated silicon nitride whiskers, which comprises the following steps: mixing refined alpha-S 3N4 powder and dispersed beta-S 3N4 whiskers to form a suspension; sequentially adding a metal nitrate solution and a precipitant solution, forming a layer of sintering aid precursor on the surfaces of the beta-S < i3N4 > whisker and the alpha-S < i3N4 >, and further performing high-temperature calcination to obtain mixed powder of the beta-S < i3N4 > whisker and the alpha-S < i3N4 > coated with an oxide sintering aid. And finally, carrying out cold isostatic pressing on the mixed powder, and carrying out air pressure sintering to prepare the high-density silicon nitride ceramic. The method provided by the invention is simple in process and low in cost, the sintering aid is introduced in a manner of coating the silicon nitride whiskers through coprecipitation, damage to the silicon nitride whiskers is effectively avoided, meanwhile, the particle size of the oxide sintering aid is finer, and the method can be popularized to preparation of other ceramic materials.

The present invention discloses a novel rotary pneumatic sintering furnace, comprising a furnace body, an inner liner, a furnace cover, a locking cover screw and a locking cover nut. Support seats are respectively provided at the left and right ends of the bottom of the furnace body. The inner liner is provided inside the furnace body. A partition is welded to the left end of the inner liner, and the partition is fixedly connected to the inner wall of the furnace body. The furnace cover is rotatably installed on the right end of the furnace body. The groove provided at the bottom of the furnace cover is movably clamped on the outside of the locking cover screw provided at the bottom right side of the furnace body. The right end of the locking cover screw is threadedly installed with a locking cover nut. A connecting pipe is provided at the top left end of the furnace body. The novel rotary pneumatic sintering furnace can realize the simultaneous firing of multiple batches of ceramic blanks, and by driving the rotary furnace frame to rotate, the ceramic blanks placed in the discharge rack can be evenly heated. At the same time, the ceramic blanks can be moved by changing their positions, which is conducive to obtaining ceramic products with more uniform structure and performance.

This invention belongs to the field of ceramic materials technology, specifically relating to photocurable silicon nitride ceramic slurry, silicon nitride ceramics, and their preparation methods. The invention involves sequentially subjecting silicon nitride powder to surface oxidation modification and sintering aid coating modification to obtain a silicon nitride composite powder with a silicon nitride core, a silicon dioxide intermediate layer, and a sintering aid outer shell. This composite powder is then uniformly mixed with a photocurable resin, a photoinitiator, and a dispersant to prepare a photocurable silicon nitride ceramic slurry. The slurry is then photocured and 3D printed to obtain a silicon nitride ceramic green body, which is subsequently subjected to thermal debinding and pressure sintering to obtain the photocurable silicon nitride ceramic. This invention, through two-step chemical modification, simultaneously optimizes the optical properties and sintering activity of silicon nitride powder, thereby improving the light transmittance of the silicon nitride ceramic slurry and enhancing the mechanical properties of the silicon nitride ceramic.

The invention provides a silicon nitride ceramic ball and a preparation method thereof. The preparation method comprises the following steps: (1) mixing alpha-silicon nitride, an additive, a binder and an organic solvent, and then sequentially performing grinding, vacuum drying, sieving and dry pressing to obtain a spherical blank; (2) carrying out shaping packaging and cold molding on the spherical blank obtained in the step (1) to obtain a silicon nitride ceramic ball biscuit; and (3) sequentially carrying out degreasing treatment, air pressure sintering and hot isostatic pressing sintering on the silicon nitride ceramic ball biscuit obtained in the step (2) to obtain the silicon nitride ceramic ball. The purpose of simply and rapidly pressing the silicon nitride ceramic ball biscuit with high sphericity degree and uniform density in batches is achieved through shaping packaging, cold molding and other molding, and the silicon nitride ceramic ball with stable quality and excellent mechanical property is obtained through air pressure sintering and hot isostatic pressing sintering; and the preparation method is high in feasibility, the forming difficulty is reduced, the balling rate is increased, and the complicated procedures of subsequent shaping are reduced.

1. The name of the product of this design: Gas pressure sintering furnace (G2 type). 2. Purpose of the product of this design: furnace equipment used for gas pressure sintering of products. 3. The design key point of this appearance design product lies in the shape. 4. The picture or photo that best illustrates the design points: Stereoscopic diagram 1.

The invention relates to the technical field of ceramic powder preparation, and discloses high-dispersity AlON powder and a synthesis method thereof and a preparation method of AlON transparent ceramic, and the preparation method comprises the following steps: (1) powder mixing: taking gamma-Al2O3 and a solid carbon source as raw materials, and carrying out ball-milling mixing on the raw materials, an auxiliary agent, a dispersing agent and absolute ethyl alcohol to obtain mixed slurry; (2) drying and sieving: drying, grinding and sieving the mixed slurry to obtain mixed powder; (3) charging and air pressure sintering: charging the mixed powder into a perforated boron nitride crucible, and performing air pressure sintering on the mixed powder in an air pressure sintering furnace to obtain high-dispersity AlON powder; and (4) carbon removal. The AlON powder synthesized by the synthesis method disclosed by the invention is of a nearly spherical single-crystal structure and has good high dispersity.

The utility model relates to the field of air pressure sintering furnaces, in particular to a high-pressure dynamic sealing device for an air pressure sintering furnace door, which comprises a furnace door insulation felt, a soaking barrel end door, a first telescopic assembly and a second telescopic assembly. Even under the condition that the furnace door is closed, the furnace door heat preservation felt can achieve the front-back telescopic function, under the high-temperature working condition, the first telescopic assembly is driven, the first telescopic assembly pushes the furnace door heat preservation felt forwards, the furnace door heat preservation felt and the furnace body heat preservation felt can form a space with better sealing performance together, and therefore the temperature uniformity of a thermal field is improved; and meanwhile, the end door of the soaking barrel can be dynamically stretched out and drawn back, the problem that the heat preservation barrel is broken due to graphite expansion is solved, the product safety is improved, the end opening sealing performance can be constantly kept through dynamic self-adjustment of the end door of the soaking barrel, the temperature uniformity of a thermal field is improved, and therefore the problem that the temperature uniformity of an air pressure sintering furnace is poor is solved.

The present invention discloses a method for preparing a high-thermal-conductivity silicon nitride ceramic toughened with boron nitride, belonging to the technical field of silicon nitride ceramics. The preparation method comprises the following steps: pretreatment of boron nitride fibers, vapor deposition, raw material mixing, compression molding, and gas pressure sintering. The vapor deposition method comprises the following steps: adopting an unbalanced magnetron sputtering method, using a boron carbide target and a magnesium oxide target as target materials to perform vapor deposition on the surface of activated boron nitride fibers. The high-thermal-conductivity silicon nitride ceramic prepared by the present invention can improve its toughness while maintaining its high thermal conductivity. The thermal conductivity of the prepared silicon nitride ceramic is 79.2-81.0 W / (m•K), the flexural strength is 738-745 MPa, and the fracture toughness is 11.3-11.6 MPa•m 1 / 2 , elastic modulus is 263~270GPa, density is 3.09~3.15g / cm 3 .

The invention relates to alpha sialon ceramic taking manganese as stable ions and a preparation method thereof. The alpha-SiAlON ceramic with the manganese as the stable ion is represented by a general formula Mnm / 2Si < 12-m-n > Al < m + n > OnN < 16-n >, m ranges from 1 to 3.6, and n ranges from 0 to 3. The novel alpha-SiAlON ceramic is prepared from Si3N4, AlN, MnO and other powder as raw materials through spark plasma sintering, air pressure sintering or hot pressed sintering and other methods, and the preparation method is simple and convenient. The alpha-SiAlON ceramic taking manganese as stable ions has high hardness and excellent fracture toughness, and is expected to be widely applied to various occasions with relatively high requirements on mechanical properties such as ceramic hardness and toughness.

The invention discloses a high-fracture-toughness silicon nitride ceramic ball and a preparation method thereof, and belongs to the field of high-performance structural ceramic materials. The ceramic ball is prepared by taking high-purity alpha-SiN powder as a matrix and adopting a composite sintering aid system composed of an oxygen-free rare earth compound, aluminum nitride and beta-SiN seed crystal through an air pressure sintering process controlled by program pressure. Under the synergistic effect of the auxiliary system and a specific process, 'bimodal distribution 'beta-SiN columnar crystals and high-melting-point and high-toughness intergranular phases are generated in situ in the material, so that the fracture toughness of the material is remarkably improved on the premise of not sacrificing hardness and strength. The fracture toughness of the silicon nitride ceramic ball is up to 8.5-11.0 MPa.m / , the bending strength is 750-1050 MPa, and the silicon nitride ceramic ball is particularly suitable for precision bearings under high-speed and high-load working conditions, such as a wind power generation main shaft, an aerospace engine main shaft and the like.

This invention relates to the field of structural ceramic materials technology, and discloses a silicon nitride-based composite ceramic material with high fracture toughness and its preparation method. The silicon nitride-based composite ceramic material with high fracture toughness comprises, by mass, the following raw materials: α‑Si3N4 70-82 parts fine powder α‑Si3N4 10-20 parts coarse flour β‑Si3N4 Seed crystals 1-4 parts Y2O3 2 ~5 parts, MgO 0.5~2.0 parts, Al2O3 0 ~1.5 parts. The preparation method includes preparing silicon nitride slurry, preparing silicon nitride composite powder with surface-loaded composite sintering aid, preparing composite particles, preparing ceramic green body, degreasing treatment, and two-stage gas pressure sintering. This invention utilizes... α‑Si3N4 fine powder and α‑Si3N4 The bimodal particle size distribution of coarse powder is beneficial to improving the packing state of raw material powder and enhancing the uniformity during molding and sintering.

The application discloses a kind of silicon nitride ceramic balls and preparation method thereof, its steps are: first with gamma-ammonia propyl triethoxysilane to alpha-silicon nitride powder is modified and is screened 0.1-0.2mm ball seed;With polyvinyl alcohol / carboxymethyl cellulose sodium aqueous solution as binder, rolling forming is obtained in sugar-coated machine silicon nitride ball blank;Again ball blank is placed in by nano silicon nitride and polyacrylic acid ethanol dispersion liquid is prepared by premixing-middle mixing-high speed dispersion enhanced mother liquor, 60-65 ℃ low speed stirring ≥8h complete enhancement;Subsequently 350-500W microwave drying 30-50min, 0.5MPa nitrogen atmosphere 1700-1750 ℃ pressure sintering 4h, finally polishing is obtained high density, high hardness, high wear resistance silicon nitride ceramic ball finished product.Innovatively proposed silicon nitride ball blank mother liquor enhancement technology, using nano silicon nitride sol as mother liquor to ball blank is maintained and enhanced, improve the density, uniformity and strength of ball blank, solve the difficulty that the strength and uniformity of rolling forming ball blank are poor.

The present invention discloses a preparation method of a high thermal conductivity silicon nitride ceramic material for lightning protection insulators, belonging to the technical field of silicon nitride ceramics. The method includes the following steps: preparing β-silicon nitride whiskers, modifying β-silicon nitride whiskers, preparing silicon nitride composite powder, cold isostatic pressing molding, and gas pressure sintering; the method for modifying β-silicon nitride whiskers is to disperse β-silicon nitride whiskers in a hydrolyzed and activated polyacrylamide solution, add a dehydrating agent N,N-dicyclohexylcarbodiimide, react at 50-60 °C for 2-3 h, after the reaction ends, filter and separate the product, wash with water and dry to obtain modified β-silicon nitride whiskers. The thermal conductivity of the silicon nitride ceramic prepared by the method of the present invention is 87.5-89.2 W / (m·K), the flexural strength is 837-850 MPa, the fracture toughness is 10.6-11.1 MPa·m 1 / 2 , and the density is 3.09-3.21 g / cm 3 .

Method for producing hard metal bodies that have a hard metal microstructure at room temperature, which is free of tungsten dicarbide and eta phase, in which LPBF, SLM, DMLS or SLS as a laser-based additive manufacturing process with energy input via laser powers of 20 W to 55 W and scan speeds of 20 mm / s to 75 mm / s and track spacings of 30 µm to 205 µm and layer thicknesses of 20 µm to 45 µm at each point of energy input to achieve a temperature of 800 °C to a maximum of < 1800 °C from hard metal granules as starting materials made of WC as a ceramic hard material with Co as a metallic binder phase and an additive of Cr3C2 and the hard metal granules have a porosity of > 0 vol.% to 40 vol.%.-%, a hard metal green body with a density of at least 50% and at most 70% of the theoretical density of the hard metal body is produced, and which is subsequently subjected to sintering at temperatures up to a maximum of 1600 °C, by means of vacuum sintering at temperatures of 1200 to 1600 °C and at partial pressures of 100 to 90000 Pa or gas pressure sintering at temperatures of 1380 to 1600 °C and pressures of 5 to 10 MPa until a density of the hard metal body of ≥ 98% to 99.9% of the theoretical density.

The invention discloses a high-performance carbon nanotube reinforced silicon nitride composite ceramic ball and a preparation method thereof. The method comprises the following steps: firstly, carrying out surface functionalization on carbon nanotubes through acidification, and then realizing highly uniform dispersion of the carbon nanotubes in SiN powder in combination with high-energy ultrasound and planetary ball milling under the protection of inert gas; then carrying out spray granulation, mould pressing and cold isostatic pressing to obtain a high-density biscuit; carrying out degreasing, air pressure sintering and hot isostatic pressing post-treatment to obtain an almost fully-dense composite material; and finally, the high-precision ceramic ball is obtained through precise grinding. According to the preparation method disclosed by the invention, through a combined sintering process of chemical-physical-mechanical synergistic dispersion and air pressure sintering-hot isostatic pressing, the problems that the carbon nanotubes are easy to agglomerate and the interface is combined and controlled are effectively solved, and the prepared composite ceramic ball has high toughness (greater than or equal to 7.5 MPa.m / ), high reliability (the Weibull modulus is greater than or equal to 15) and long fatigue life; the method is suitable for the high-end equipment manufacturing field.

The invention belongs to the technical field of ceramic material preparation, and provides a high-thermal-conductivity silicon nitride ceramic substrate and a preparation method thereof. According to the method, a high-entropy oxide sintering aid is prepared through a coprecipitation calcination method, titanium hybrid polycarbosilane is chemically synthesized to serve as a functional aid, and meanwhile silicon nitride powder is subjected to surface coating modification; the preparation method comprises the following steps: uniformly mixing modified silicon nitride powder with the two assistants, carrying out tape casting to obtain a biscuit, carrying out multi-stage air pressure sintering on the biscuit, regulating and controlling atmosphere, pressure and temperature in a sintering procedure, completing low-temperature treatment, vacuum sintering, high-pressure densification and high-temperature and high-pressure sintering step by step, and carrying out specific annealing treatment in a cooling stage to obtain the silicon nitride ceramic. According to the invention, by utilizing the synergistic effect of the compound additive and a precise sintering schedule, the growth of silicon nitride grains is effectively promoted, and the grain boundary phase is optimized, so that the prepared silicon nitride ceramic substrate is highly compact in structure and pure in grain boundary, and excellent heat-conducting property is realized.